In a known screen each screen deck is fixed above cross beams of the deck. The cross beams, fixed at their ends to the body, are arranged crosswise relative to the direction of movement of the material to be screened. The successive cross beams are connected to each other by longitudinal supports which are arranged in the movement direction of the material to be screened that is parallel to the length of the screen. A screening means forming the screen deck is formed for example of a mesh or a perforated plate. The screen decks are tensioned on the longitudinal supports and tensioned from perimeters of the screen deck to the body at the sides, for example, to a side plate comprised by the body. A known four-deck screen is shown in FIG. 1. Own cross beams are required for each screen deck. There is required much space between the decks in the known solution that a change of a screen mesh is possible. Therefore, screens with several decks are very high and heavy. The large height is complicating handling and transport of mineral material processing apparatuses, increasing the height of mineral material processing apparatuses, and the loading height of the screen may become high. Placing to an allowable load height, particularly of wheel based screening plants towable on road or track based screening plants transportable on a carriage, is often complicated in case of multi-deck screens.
In this connection mineral material means soil, for example, rock material, which is gained from the earth by excavating, exploding or crushing, and construction material such as bricks and concrete.
An object of the invention is to create a screen solution by which problems of the prior art can be eliminated or at least reduced. A particular object is to lower a screening apparatus. A particular object is to lighten a screening apparatus. A particular object is to create a multipurpose screen module having a simple construction. A particular object is to simplify change of a screening means. A particular object is to reduce material used and work in production and maintenance of a screen apparatus.